It is well-known that lenses, and in particular spectacle lenses, comprise an ophthalmic substrate having geometrical features adapted to the wearer.
It is a common practice in the art to coat at least one main surface of the ophthalmic substrate with several coatings for imparting to the finished lens additional or improved optical, mechanical properties and/or surface chemistry. These coatings are designated in general as functional coatings.
Thus, it is usual practice to add functional coatings, for instance an anti-abrasive coating to increase the abrasion resistance of the lens, an anti-reflective coating to decrease the reflection of light and an anti-soiling coating applied over the anti-reflective coating. The anti-soiling coating provides an outer coating that can be more resistant to contamination for instance by organic impurities and more easily cleaned than the anti-reflective coating. The anti-soiling coating furthermore protects the anti-reflective coating.
Furthermore, the wearer of the lens can wish to replace or review such an anti-soiling coating because the effects of said coating can decrease over time.
Other coatings such as a polarized coating, a photochromic or a dyeing coating may also be applied onto one or both surfaces of the lens substrate.
Another example of coatings is an anti-fog coating which can provide an anti-fog function for a temporary need, for example in winter period.
In consequence, there is a need for a method suitable for the addition of a functional coating on an optical surface of a spectacle lens in a delayed way after their design and their arrangement in a spectacle frame or at the request of the wearer. More particularly there is a need for a method suitable for the addition of a functional coating on an optical surface of a spectacle lens after their manufacturing or design and their arrangement in a spectacle frame, or at the request of the wearer to upgrade or modify their performance characteristics.
In view of the fast development in the top coat technology, it would be of interest to be able to safely add or replace an initially deposited top coat by a new top coat having different or improved properties.
So, the invention is directed to a method for loading or reloading a functional coating on an optical surface of a spectacle lens. This method is simple and can be implemented by a single compact machine in order to be placed at an eye care practitioner's premises and used directly by the eye care practitioner (ECP).